The relationship between the morphology of mandibular symphysis and the craniofacial morphology in class lll malocclusion

Kim, Sang Doo; Kwon, Oh Won; Sung, Jae Hyun

Abstract

By studying the relationship between the morphology of mandibular symphysis and craniofacial morphology in class III malocclusion, this study aims at deciding whether the morphogy of mandibular symphysis can be used as a predictor on the growth of mandible. The materials used for this study were the cephalometric radiographs of male class III malocclusion. The subjected age groups were 10-12(G1 group) and 20 and above(G2 group); 50 were selected from each group. Each group was again divided, according to the ratio of symphysis, into Large(L), Average(A), and Small(S). The results of this study were summarized as follows: 1. In average the ratio of symphysis, G2 group showed significantly bigger than G1 group(P<0.05). 2. In both GI and G2 groups, the ratio of symphysis had no relationship with the measurements on the cranial base and the maxilla(P>0.05). 3. In both G1 and G2 groups, there was not distinct difference in the antero-posterior positions among L, A, S subgroups. 4. L and A subgroups showed significantly larger than S subgroup in lower gonial angle and chin angle in G1 group (P<0.05) 5. In the measurements on the vertical relation of the face, anterior total face height(ATFH) and anterior lower face height(ALFH) of L subgroup were significantly larger than that of S subgroup in G1 group(P<0.05) and also mandible showed a tendency to grow downward vertically. 6. In the measurements on the tooth position and inclination, L subgroup showed as compared with S subgroup a tendency of extrusion of maxillary and mandibular teeth in G1 group, but G2 group showed such tendency only in mandibular teeth. 7. In the measurements on the abnormal growth prediction by Schulhof, in G1, there was no significant difference among L, A, S sugroups. 8. In the correlative analysis of the ratio of symphysis and other measurements, G1 group showed significant correlationships in chin angle, PP/MP angle, ANS-Me and other, while G2 group showed the same only in MP-LIT and MP-LMMC(P<0.05, P<0.01). In summarizing the above, in the G1 group, consisting of young males, no difference was noted in horizontal relation between L and S subgroups; in vertical relation, L subgroup showed a stronger tendency of downward growth of mandible than S subgroup. In adult male G2 group, however, no distinct morphological difference of craniofacial complex by the ratio of symphysis.